According to survey of the Japanese Ministry of Health, Labor and Welfare, it has been reported that the number of patients suffering from periodontal disease accounted for 18.2% of the national population according to the survey in 1975, but increased to 68.1% in 1993 and 72.9% in 1999, thereafter the number has increased steadily, and the presumed number of the patients has reached even 90 millions, and the current situation is that much expenditure is imposed on the dental region also from the viewpoint of medical economy.
For that reason, the authority has already decided to address prevention of periodontal disease in a nationwide scale in 1988, and has been working on development and promotion of the so-called “8020 movement”.
However, currently, the number of patients has not decreased yet, and development of breakthrough methods for prevention and treatment of the disease are desired.
In recent years, it is pointed out that periodontal disease is not merely a disease as chronic infectious disease of the gingival tissues, but has a risk of causing circulatory system diseases such as cardiac infarct and destruction of blood vessel due to aneurysm, and periodontal disease also attract attentions as a risky factor for induction of diabetes mellitus and premature delivery. For treatment of periodontal disease, there has been no appropriate therapy so far, and treatment by dental techniques, that is, administration of germicides to a pathological site, surgical operation, oral administration of antibiotics and so forth, are practically used. However, long term consecutive administration of germicides or antibiotics for therapeutic treatment generates novel resistant bacteria due to the use thereof, and at the same time, it has many serious problems such as development of side effects due to the drug. Thus, it is the present situation that any satisfactory treatment method has not been necessarily established.
Therefore, for the purpose of prevention and treatment of periodontal disease or caries, the possibility of prevention or treatment of the aforementioned diseases by use of lactic acid bacteria has been studied as a method alternative to the administration of germicides or antibiotics.
As methods for prevention and treatment of periodontal disease and caries using lactic acid bacteria, a method of using, as an active ingredient, cells and/or aqueous extract of Enterococcus faecium, Streptococcus equinus, Lactobacillus fermentum or Lactobacillus salivarius are disclosed in Japanese Patent Laid-open Publication (Kokai) No. 61-91126 and Japanese Patent Publication (Kokoku) No. 4-52249. Further, in International Patent Publication WO99/07826, factors for suppressing the inhibitory activity for glucosyl transferase expressed or produced by Lactobacillus spp. V20 and Streptococcus oralis and development of caries, and the aforementioned lactic acid bacteria inhibiting production of hydrogen peroxide are studied.
Meanwhile, 400 or more kinds of bacteria inhabit in the human oral cavity, and the number of bacteria reaches even 10 billions. Incidentally, a number of bacteria at a level of 108 to 109 CFU/ml is detected in saliva. Therefore, a complicated microflora is formed in the human oral cavity (oral microbial flora), and thus it is extremely problematic to discuss effectiveness of prevention and treatment of periodontal disease and caries in humans based on extrapolation of results obtained in a simple in vitro system. In addition, in order to discuss the effectiveness on the premise of administration to human, it is necessary to also consider viability of live bacteria in a live bacterium preparation or food containing a lactic acid bacterium, as well as flavor and physicochemical properties of such a live bacterium preparation or food containing a lactic acid bacterium. However, in the aforementioned literatures concerning utilization of lactic acid bacteria in prevention and treatment of periodontal disease and caries, data of elimination or suppression of pathogenic bacteria of periodontal disease or caries obtained in an in vivo system using human or model animal, or data concerning viability of live bacteria in a live bacterium preparation or food containing a lactic acid bacterium, flavor and physicochemical properties of such a live bacterium preparation or food containing lactic acid bacterium are not disclosed at all.
As a bacterial strain used in a live bacterium preparation or food containing a lactic acid bacterium serving as means for prevention and treatment of periodontal disease and caries, of which administration to human is intended, a lactic acid bacterium strain that can definitely eliminate or suppress pathogenic bacteria of periodontal disease and caries, which are intraoral pathogenic bacteria, in a test using human and model animals should be selected. Further, when the lactic acid bacterium strain is used in a live bacterium preparation or food containing the lactic acid bacterium, it is essential that the lactic acid bacterium should show high viability, and it is preferred that the preparation or food shows superior flavor and physicochemical properties.